Pre-heat your oven to 400 F and prepare 2 mini cupcake pans with mini cupcake liners. Set aside.

In a separate bowl, mix the dry ingredients (flour, baking powder, baking soda, salt and natural unsweetened cocoa powder). Over a large bowl, beat sugar and butter with an electric mixer for 1 minute on medium-high speed. Mixture should resemble light wet sand. Add the egg and mix.

Start adding the flour mixture to the wet ingredients, alternating with milk, and beat on medium speed until fully combined. Beat for 1 more minute. Add vanilla extract and coffee and mix until just combined. Mixture will be very thin.

Fill mini liners 2/3 full and bake for 5 minutes. Reduce temperature to 350 F and bake for an additional 7-8 minutes, or until a toothpick inserted in the middle comes out clean.

Let cupcakes cool a bit in the mini cupcake pan -around 5 minutes-, then remove them from the pan really carefully (they will be very soft!) and place them over a cooling rack to cool completely before frosting.

To make the frosting, beat butter until creamy, about 1 minute. Add powdered sugar, cocoa powder, melted chocolate, vanilla extract and salt. Beat on low speed until just incorporated, then beat in medium speed. Mixture will look dry and crumbly.

Add heavy whipping cream and beat for additional 1.5 minutes. Scrape the bottom and sides of the bowl, and beat for an additional 1.5 minutes, or until light and fluffy. Add more cream (gradually) if you want a softer consistency on your frosting.

Fill a piping bag with the chocolate frosting, then pipe it on top of your cooled cupcakes and decorate with sprinkles